Question

find the missing number in 25, 38, _, 64, -27, 90 a) -1 b) 51 c) 39 d) -32

Answer 1

Correct sequence be :

         25, 38, __, 64, 77, 90

So, we need to find a number for the blank place which satisfies the sequence

1st term = 25 & 2nd term = 38

    Difference = 2nd term - 1st term

    = 38 - 25 = 13

4th term = 64, 5th term = 77 & 6th term = 90

    Difference = 5th term - 4th term

    = 77 - 64 = 13

    Difference = 6th term - 5th term

    = 90 - 77 = 13

Thus we see that the difference between a term and its previous term is 13

So, the number to be put in blank place

    = 38 + 13 = 51

∴ option (b) is correct

Note :

  The given sequence is in Arithmetic Progression whose 1st term is 25, last term is 90 and the common difference is 13

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Answer 2

Answer:

answer is -1

Step-by-step explanation:

given sequence: 25 , 38, x , 64, -27, 90

as we have both positive and negative nos in the sequence,

the sequence logic contains both addition and subtraction.

logic:

seq:         25           38                x                    64               -27               90

diff:                +13        leave this     leave this            -91               +117

logic:           13 x(+1)                                                 13 x (-7)           13 x (+9)

we observe that it is 13 multipled by odd nos with alternate + and -

so the term next to 38 would be = 38+(13 x (-3)) = 38-39 = -1